the major health headline tonight, and it involves a very popular diet, the mediterranean diet. And what we've learned tonight is that in the middle of a new study, researchers were so astounded by what they found, they halted the study, made it public and jumped on the diet themselves. It looked at people at very high risk of heart disease and it reduced that risk by nearly a third. Let's bring in dr. Richard besser tonight. Rich, you've done many studies yourself. How common is it that you would stop before it's even done? Reporter: This is really unusual. So are the results. They found reduction of 30%. If you think about statins, that only reduces your risk of heart disease by 25%. So, this diet even better than the statins. For people at home tonight, the bottom line, remind them what the diet inclaudes. Reporter: It's rich in fresh fruit and vegetables, fish and chicken and beans. And then you want oils that are healthy. You talk about healthy oils, we all think of olive oil. We didn't know how much of it. Reporter: Yeah, in this study, each day, people were to consume four tablespoons of olive oil. That's a lot. Four tablespoons. How much in a month? Reporter: Two liters per month. A lot of oil. And the nuts right here, always worried about gaining weight, but you say this is healthy fat. Reporter: The fat in nuts will actually fill you up so you eat less. This is what you're supposed to have every day. That's a one-month supply of nuts. Rich besser, thank you. And as you know, one of the most

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